Differential-pressure recorder.



J. G. PEW & H. C. COOPER.

DIFFERENTIAL PRESSURE RECORDER.

APPLICATION TILED 39.11.15, 1912v Patented Apr. 8, 1918.

2 SHEETSSHEET l.

WITNESSES:

(Wu/wan;

J. G. PEW & H. C. COOPER.

DIFFERENTIAL PRESSURE RECORDER.

APPLICATION TILED JAN.15. 1912.

Patented Apr. 8, 1913.

2 SHEETS-SHEET 2.

NVENTORS UNIClE11...STATES PATENT OFFI E JOHN G. raw AND HOWELLLC. coornn. or rrrirsnnnen, ramsirtvamm nrrrEnENrrIAL rREssURE RECORDER,

To all whom it may concern Be it known that we, JOHN G. Pew and HOWELL C. Ooornn, residing at Pittsburgh, in the. .county of Allegheny and State of Pennsylvania, citizens of the United States, have invented or discovered certain new and useful Improvements in Differential-Pres- -sure Recorders, of which improvement the and pressure recorder are shown in section;

gas, such difference being caused by the and Fig. 2 shows, in a similar alternate form of the invention.

In the practice of the invention, a gasoonduit 1 has connected thereto a pressurerecording device in such a manner as to record the difference in the pressures of the gas manner, an

flpwing through the conduit.

In the preferred form of the invention the gas pipe 1 is provided with a transverse orificed-abutment. In order to have gas flow through the orifice of the abutment, the static pressure of the gas on the downstream side of the abutment must be less than that on the up-stream side; and, it will be understood, that the amount of gas flowing through the orifice will be proportional to the square of such difference in static pressure, provided the gas on the rip-stream side of the abutment remains at a (.OliSlflllil pressure. Such a means for measuring the volume of a body of flowing gas is illustrated in Fig. l. The conduit may be divided at a point where it is desirable to measure the volume of the gas flowing therethrou h. Suitable internally-threaded shoul ered flanges2, 3 may be secured, one to each end of the divided conduit; and an abutment or disk 4, having an orifice 5 of known cross-sectional area, may be clamped between the said flanges, as by bolts 6. Pipes 7 and 8 may be connected at one end to the right and left side respectively of the abutment 4,-a'n'd at the other ends'to a, suit able diiferent-ial pressure recordm'. As'.

Specification of Letters Patent. Application filed January 15, 1912; Serial No. 671,223.

shown herein, the pipes-fimd 8 are prefer ably secured in suitably provided holes in the flanges 2, 3. a The pressure recorder which is preferably used, consists of a casing 9, 10, 11 inclosing within its walls three chambers. The chamber 12 may be formed of the casing-portion 9 and the partition 13; the chamber 14' may be formed-of the casing-portions 10, lfiand the partition 13; and i the chamber 15, placed within the chamber 14 is preferably the expansible chamber of what is commonly known as a Bristol recording gage. Such a recording gage consists of the said cxpansible chamber 15 adapted to expand by the pressure of a fluid contained therein acting against'the resistance of the said chamber and whatever pressure there may be in the mediumsurrounding the said chamber. As the said chamber 15 expands,

it moves upward, and by such movement 7 causes a pencil-provided indicator hand 17 to move over the face-offend trace a line upon, a dial 18, which may he -uniformly moved, as by a cloclnvork 19. In the construction shown herein the said expansible chamber 15 is connected, as'by pipe 20, to the gas chamber 12. Furthermore the chambers 12 and 14 are of suehsize as to deaden the eli'ect of small and frequent variation in the static pressure of the gas flowing through the conduit.

The casing parts 9 and 10 may be Suitably united by bolts 24, and the lid or cover 11 may be removably secured to the casin portion 10, to the end that access may be had to the pressure recorder. The-pipes 7 and 8 may be provided with valves 25- and 26, so that communication between the conduit 1 and the chambers 12 andl't'may be closed at such times as may be desirable. Also the pipes 7 and 8 may be connected bya ipe 27, provided with valves 28 and with a branch valve-controlled pipe 29. In the operation of the invention as thus far described, gas from the right of the abutment 4 flows through the pipe 7 and fills the chamber 12, the static pressure of such gas being the same as that in the pipe 1 to the right of the said abutment. 'Also as from the left of the said abutment will ow through the pipe 8 and will fill the chamber 14-with gas at'thesame'wic; the 'ga 'in'the conldiiit Widths Patented Apr. I-

chamber 12 is greater than that mchamb'er said abutment. The ex ansible chamber 15 bein connected to the chamber 12, gas from the first named chamber will flow into the chamber 15 at such times as the ressure in 14:- Such difference in pressures between the as in the chambers 11 and 15 will c'ausethe" atter chamber to expand in proportion-t0;

the said difference in pressures. The movement of thesaid expansible chamber,- will, as described, cause the, indicator hand 17 {to trace, ina manner "wellundersto'od by.,tl1ose skilled in the art, a line uponthe uniformly moving dial l8. S'uch'a line will indicate the continuous or varying difference, in. pressures of the gas to theright and left of the abutment it; so that, knowing thelcrosssectional area'fof the orifice 5 thevolumecf therethrough for any, given pelie computed, 'Whenit, becomes gas flowin riod" may desirable to remove' 'the cover 11, as for changing the recording dial, the valves 25' and 26 are closed and theyalves 28 are; opened in order'to equalizethepressures 'the'chambers12, Hand 15 The valve 30 of} the pipe 29 may then belopenedto relieve the pressure in the said chamberslan'd the cover 11' may then be readily removed, i Suclrbeing the operation of the preferred form of our invention as thus {far described, we-willjnow proceed to describeadditional stood that such a'record "will give the, varia.-:

tions-in the absolute pressure of ,the gas to the right of the abutment 4, and thatsuch dataimay be used'in computingthe-volu metric flow of gaswhen its absolute pressure varies.

ative, when (by reason of a1r.emergency) the-jditfere'nce in pressure of gas above and.

below the abutmentd greater than. maybe" recorded by the f-pa'rticular I instrument; used, linens are provided to reduce such .ex-.. cessive difference in pressure. Preferablysuch a pressure rducing means/consists of anautomatically,Tcstdrable seal extending; b'etweenithechambers 12 and 14. Referring; particularly to Fig. '1', a. tU-shaped v,tube 3L may connect'the' chambers 12 and 14, as shown, the tube lying substantially in a ver- 1 in; the gabsolute static 7 Furthermore, in' order ,to avoid breaking the GX P ZLIISIblG chamber .15, or-

f tp p '22s to the otherwis ende m e, Reorder nope-1L;

tical plane and provided with an enlarged reservoir rtion 32. A suitablequantity of liquid, su irasmrcur ma be placed in the said tubeijl, asisindicated at 33, to the end that,=whn*'tlie gas ressure in the chamber 12 exceeds that in t e chamber ,14 to such a degreeth'at the recording instrumentm'ay be injured, -the-fiuid 33 will be blown out of the tube 31 and into the reservoir 32, which has sutficient capacity to containall the said ,fluid and permit1=the,.-higherpressure gas to blow therethrough, thus -.redu'cing the differ ence in pressures between. the said cha'mbers 12 L and 1 4, s It; i will be understood -;0f' this construction i that, when i the normal difference in pressures has been restored the' liquid will return to the; tube. 31- .andthus: form an effective seal against the further: flow of gas 5 from. the .qhambenrl2 through-the tube 31"" an in the chamber -14.- @I.

n In the form.lofsthe.invention 'shownin; 'Fig'. 2,- the-.difi'er'entiala pressure recorder is arranged ,to .record {the;- difference 5 between 11 6351 111 0f;thestatic,;and dynamic pressures and the static ipressure alone :of a body of gas ,flowingi it-hrough a pipe of known i-cross sectional area To 'such an end a Pitot tube 23 may be suitably" connected 1 to the conduit 1?, thatubfi openin inlthedirectionopposed to the flow of gas through the said-conduit; and pipes: {Hand-=8? may beconnected at conduitjlfi respectively, and at their' up er ends tothe chambers l2 -and 14 ofa di erential recorder; constructed the same a heretofore described; I In this construction the gas withinthe chambers 12 and 15* will, whengasisflowing through the conduit 1 be, at agreaterr pressure than the gas in the chamber, 14;, the difference in pressures beingproportionalto the square of the velocity of flow through; the; said =c'on'duit, as is well understood bylthose skilled in the-artfi Furiel'r lower ends to the Pitot tube 23 andthe thermore, the; chamber: 15 will" expand as heretofore described, and a record of the vrmying (in-constant differential pressurewill b e,made,.upon the dialt' In orde'rto-obtain a .re'cqrdof whatever variations there may be flowing-vgthrough' the plpe l, a second recording-instrument 21 may 'be-connected "as pipe 8, the '-operation of such; a recorder being the same as that 'de scribedin connection withjtl erecorder 21,

shown-in Fig.- 1..-: a

- JVe do: not wish to linrit= j oui"selve s to the details of construction shown :an'd' described :herein; for; obviously many'ehagges may be madeby those skilled infthe art without de- .-.;We claim ias our invention .umetric I binatlon of a shell or" case divide into two chambers by a partiti'bn, an e'xpansible ch ainpartingiro m the spirit-ofpur invention. I

; .lnsangzst'rument for-determiningthe'vol W101i 9. 'gaszin-"a cor'dui ,the com pressure qf the gas I said chambers Within the casing, an" indi- 1,e5s,ce2 her in one of said chambers communicating In testimony whereof we have hereunte with the other of the two said chambers, set our hands. 7 connections from the conduit to each of the JOHN g PEW- .7 P1 P1 g1 CfllZOl hand Within the said shell secured to said expansible chamber, and a dial Within Witnesses: the said shell movable with relation to said PAUL N. lamcmlow, hand, substantially as described. FRANCIS J. Torymssou. 

